The provision of abradable material, in the compressor or turbine section of a gas turbine engine for example, is known. For instance a rotor made up of a plurality of blades is contained within a casing or shroud surrounding the blade tips, and a coating of abradable material may be provided on the inner surface of the surrounding casing or shroud. As the rotor rotates, the rotor blades may experience deflection or movement during operation of the engine, due to factors such as loads, shaft deflection, thermal growth, bearing failure, foreign object damage, etc. This deflection or movement can cause the outer tips of the rotor blades to rub against the abradable material of the casing and carve precisely defined grooves in the abradable material coating without contacting the outer casing or shroud itself.
This may help maintain an acceptable tip clearance for aerodynamic performance purposes, while preventing unnecessary contact between the outer casing or shroud itself and the blade rotors. However, as a result of the rubbing contact between the rotor blades and the abradable material, the rotor blades may nevertheless experience important rubbing loads that are consequently imparted to the rotor blades. These loads can stress the rotor blades and may lead to reduced lifespan of the rotor blades.